from Guyton and Hall textbook of medical physiology, 4th South Asia ed

from Guyton and Hall textbook of medical physiology, 4th South Asia edition write a 3 -mark reasoning answer on why resection of terminal ileum produces megaloblastic anemia。

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Guyton Hall medical physiology vitamin B12 terminal ileum absorption intrinsic factor megaloblastic anemia

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"Vitamin B 12 Deficiency"[MeSH Terms] AND "Megaloblastic Anemia"[MeSH Terms]

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Resection of the terminal ileum causes megaloblastic anemia because vitamin B12 absorption is impaired. Vitamin B12 normally binds intrinsic factor and the complex attaches to specific receptors on ileal mucosal cells for absorption. Loss of the terminal ileum therefore causes vitamin B12 deficiency. Since vitamin B12 is required for thymidine triphosphate formation and DNA synthesis in rapidly dividing erythroblasts, nuclear maturation and cell division fail. The marrow produces large, poorly developed macrocytic cells, resulting in megaloblastic anemia. Body B12 stores are large, so anemia may appear only after several years.

Source: Guyton and Hall Textbook of Medical Physiology, section “Maturation of Red Blood Cells Requires Vitamin B12 and Folic Acid,” library lines 3799-3818.

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